1. Field of the Invention
This invention relates in a general way to the measurement of an energy flux and in particular to the measurement of a heat flux, i.e., to the determination of the amount of heat that passes per unit of time and surface through a wall and to the measurement of visible or infrared radiation and further relates to a device for measuring an energy flux comprising a heat flux meter, i.e., a heat flux measuring apparatus, used particularly for measuring the conductivity or thermal resistance of insulating materials or construction elements.
2. Discussion of the Background
It is known that the measurement of the thermal properties of some light and thick insulating materials requires the use of a device of the type indicated above which has a large measuring surface.
Several types of heat flux meters have already been developed to make these measurements. One of these flux meters, described in European Pat. No. 0003271, comprises a substrate of electrical insulating material in which a network of through holes and several thermocouples associated in series are provided. The hot and cold junctions of the thermocouples are metal coatings, particularly of copper and nickel respectively, deposited on the opposite faces of the substrate while the conductors of each thermocouple are formed by metal coatings deposited respectively on the opposite faces of the substrate and on the walls of the adjacent holes which go through said substrate, on the one hand, to connect the hot and cold junctions to one another and, on the other hand, to connect the thermocouples in series.
It is then possible to take at the terminals of this circuit in series a voltage that is the sum of the electromotive forces generated by all the thermocouples and which is a function of the difference between the temperatures prevailing respectively on both sides of the substrate.
With the value of this voltage it is possible to determine the heat flux going through the flux meter in a way known in the art.
This flux meter already represented a great step in comparison with previous flux meters in which the conductors consisted of sections of wire inserted in the substrate holes and then soldered at suitable locations. Actually, it eliminated the wires requiring spot manual placing and soldering operations by using metal deposits that can be performed in the aggregate, i.e., without spot operations and automatically by more reliable, perfectly reproducible metal-coating and photoetching techniques making it possible to increase the number of junctions without increasing manufacturing work. This results in:
the possibility of making flux meters with large surfaces and various shapes, fast series manufacturing with good geometric or electric reproducibility, PA1 uniformity in making the junctions, PA1 absence of excess thickness on the faces of the substrate by elimination of soldering, PA1 a great sensitivity by increasing the density of the junctions, i.e., increasing the number of junctions per unit of surface, PA1 an integration of the surface temperature with metal strips forming surface conductors and making of two planes constituting the hot and cold faces of the substrate, these two planes exhibiting a better isothermicity.
However, for reasons of convenience and cost in making metal deposits, in particular on the walls of holes that go through the substrate, reasons that essentially relate to the fact that metal-coating shops, developed above all for making printed circuits, are not currently equipped for depositing some metals, the choice of metals to be deposited is limited and in making these flux meters metal couples must often be chosen whose thermoelectrical output is not necessarily the best.
Further, the flux meter described above has holes alternately coated with one metal and the other metal of the thermocouple, which complicates manufacturing.
Moreover, the risk of creating heat short circuits by multiplying the number of junctions per unit of surface limits the increase in the sensitivity.